The invention relates to a battery clamp with which a usually conical battery contact consisting of lead can be contacted.
The problem occurring when such a battery contact is contacted consists in observing a defined contact force as precisely as possible for the reliable contacting. In case the contact forces are too small, only insufficient metallic contact results between the battery contact and the battery clamp. However, if the contact forces are excessively great, this will lead to a deformation and the flowing of the battery contact material.
The most common battery clamp consists of a contact clip which is placed onto the battery contact and is then pulled together by means of a screw. The drawback of this kind of battery clamp is that the actually applied contact force can be controlled only insufficiently. On the one hand, there is the danger that by tightening the screw with a wrench a much greater tightening torque and thus a much greater contact force is applied than actually required. On the other hand there is the danger that if the battery clamp is used for an already deformed battery contact the contact clip will be pulled to block by the screw so that a high tightening moment for the screw is obtained, which, however, does not correspond with the actually obtained smaller contact force.
The prior art also discloses various battery clamps which use spring elements which are to ensure a constant contact force. However, these battery clamps have a comparatively complex design.
The object of the invention consists in providing a battery clamp which can be produced simply and in cost-effective manner and is simultaneously fail-safe in handling, i.e. can be mounted both manually and in automated fashion with a high degree of reliability without incorrect mounting occurring, and which can be detached again with low effort.
This object is achieved in a battery clamp comprising a connecting lug, a contact ring which is provided with a slot so as to form two opposite clamping ends, and a spring which engages the clamping ends of the contact ring. The battery clamp further comprises a blocking wedge which can be shifted between a contact position in which it releases the clamping ends such that the spring can pull the clamping ends together, a mounting position in which it keeps the clamping ends of the contact ring to be spread apart such that the battery clamp can be placed on the battery contact, and a pull-off position in which it spreads the clamping ends of the contact ring to a larger degree than in the mounting position such that the battery clamp can be pulled off from the battery contact. Thus, three defined states of the battery clamp are possible. In the mounting position the battery clamp can be slipped freely on the conical battery contact until the contact ring abuts in planar fashion against the battery contact. In the contact position the contact ring is resiliently pulled together around the battery contact. The contact force applied in this case is determined by the spring design and in this connection remains constant even over a prolonged period of time because of the resilient bias applied by the spring. In the pull-off position the contact ring is spread to a larger degree as is the case on mounting. This ensures that the battery clamp can easily be pulled off, despite a possible settling phenomenon in the mounted state and despite a possible prestress which is applied on the contact ring during mounting.
According to a preferred embodiment of the invention, each clamping end is provided with a bent-off lug which comprises a first slope each and the blocking wedge is arranged between the lugs of the clamping ends. With this design, a translatory motion of the blocking wedge, which can be achieved simply, suffices to spread the contact ring from the contact position into the mounting position.
According to the preferred embodiment of the invention each lug is provided with an arresting edge. The blocking wedge can support on this arresting edge if it is in its mounting position in which the clamping ends of the contact ring are held in a spread condition. In this way, a comparatively great actuation force is required to move the blocking wedge beyond the arresting edge to reach the clamping position; this ensures that unintended transfer of the battery clamp from the mounting position to the contact position is prevented. The great actuation force to be applied also results in an advantageous kind of battery clamp mounting. If the arresting edge is designed to be sharp-edged, as is preferred, the blocking wedge cannot be moved beyond the arresting edge by a mere force of pressure. This will only be possible if the clamping ends were slightly spread beforehand. This can be achieved by forcing the battery clamp, being in the mounting position, onto the conical battery contact. The contact ring is spread slightly by the conical battery contact not until the battery clamp is forced onto the battery contact by the application of a defined force, so that planar contact results. Then, the spreading wedge can slip over the arresting edge and release the clamping ends of the contact ring, so that the spring can pull the clamping ends together. The final contact force is thus determined exclusively by the spring design, however the preceding forcing of the battery clamp onto the battery contact ensuring that planar contact occurs between the battery contact and the contact ring. This results in a high mounting reliability, since the transfer of the blocking wedge from its mounting position to its contact position will not be possible until it is signaled by the corresponding spreading of the contact ring that a defined previous contact force was built up between the contact ring and the battery contact. This previous contact force ensures a reliable fit of the battery clamp, since the regions of a point contact of the battery contact are eliminated by the flowing of the material already when forcing on the battery clamp.
According to a preferred embodiment of the invention it is provided for that each lug is additionally provided with a second slope which, as seen from the first slope, lies behind the arresting edge, the minimal distance between the two opposite second slopes being smaller than the distance between the two opposite arresting edges. With this design, the pull-off position can easily be brought about in that the blocking wedge is pulled from the contact position beyond the arresting edge as far as into the region of the second slope. As the two second slopes lie closer to each other than do the two arresting edges, it is ensured that the contact ring is spread in the pull-off position to a larger degree than during mounting; during mounting the contact ring is spread just so much that the blocking wedge can slip through the two arresting edges.
According to the preferred embodiment of the invention it is provided for that the blocking wedge is connected with a shiftily mounted covering cap. The covering cap serves both as a protection for the battery clamp and a mounting aid. The covering cap offers a suitable pressure surface area in order to apply the required putting-on force by hand. The force of pressure exerted on the covering cap simultaneously serves for transferring the blocking wedge from the mounting position to the contact position. Since the putting-on of the battery clamp and the subsequent locking by transferring the blocking wedge from the mounting position to the contact position is effected in a single direction, mounting can be automated easily. Manual mounting does not cause any problems either, since it only consists of forcing the battery clamp onto the battery contact. In both cases, the jolting overcoming of the arresting edge by the blocking wedge represents a well noticeable indication of the fact that the mounting has been concluded successfully in both automated and manual mounting.
According to the preferred embodiment, the contact ring is provided with at least one recess, and a key lug is provided on the covering cap. The key lug can rest against an edge of the recess and prevents a movement of the blocking wedge into the contact position if there is not arranged a battery contact in the interior of the contact ring. In this way, it is ensured that the blocking wedge cannot unintentionally reach the contact position, e.g. during transport, which would mean that the subsequent mounting of the battery clamp is not possible.
The key lug preferably extends along the direction of movement of the blocking wedge, and is provided with two sloped surfaces which cooperate with a slope on the edge of the recess. This alignment of the key lug results in a high load carrying ability when there is a pressure exerted on the covering cap, and the slope surfaces are arranged such that the holding force of the key lug in the recess is increased with such pressure.
According to an alternative embodiment the key lugs may also be arranged perpendicularly to the direction of movement of the blocking wedge, i.e. horizontally on the covering cap. This offers advantages with regard to the elasticity and the required and allowable spring excursion.
It is preferred that a lever is supported on the covering cap, which rests against the contact ring and by means of which the blocking wedge can be brought from the contact position via the mounting position into the pull-off position. The lever, when suitably supported, must only be lifted upwards and away from the battery contact, whereby both the transfer of the contact ring from the contact position to the pull-off position and the lifting of the battery clamp from the battery contact is obtained by means of a motion in a single direction. As an alternative to the lever it is also possible to use an eccentric which can spread the lugs of the contact ring by a rotary motion and release them again.
Preferably, the lever is provided with a first support surface which can rest against the contact ring, and with a second support surface which, as seen from the axis of rotation of the lever, lies outside the first support surface, a contact area being formed between the first and second support surfaces. The contact area can get into contact with a suitable contact step on the contact ring and reliably prevents that the lever is xe2x80x9coverstretchedxe2x80x9d, i.e. is pivoted exceedingly far.
Preferably, the spring is provided with a holding lug and the blocking wedge is provided with a holding projection which is able to get into contact with the holding lug and limits the shift length of the blocking wedge. The holding projection is here preferably designed such that it snaps into place behind the holding lug during mounting the covering cap to the contact ring, by this lug being bent elastically outwards.
According to a preferred embodiment of the invention the inner side of the contact ring is provided with a knurling. This ensures a reliable fit of the contact ring on the conical battery contact so that the contact ring cannot xe2x80x9cfloat awayxe2x80x9d upwardly. As an alternative, grooves may further be provided which run along the longitudinal direction of the battery contact and provide sufficient mechanical friction between the battery contact and the contact ring.
Advantageous embodiments of the invention will be apparent from the subclaims.